Diaphragm unit



Sept. 4, 1951 1.. HORNBOSTEL DIAPHRAGM UNIT 4 Sheets-Sheet 1 Filed July 30, 1945 r L. i

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DIAPHRAGM UNIT Filed July so, 1945 4 Sheets-Sheet 2 A 1. 0 o flalewaas TEL Sept. 4, 1951 L. HORNBOSTEL 2,567,151 7 DIAPHRAGM UNIT Filed July 30, 1945 4 Sheets-Sheet 5 Ill/Ill f7 V527 [SF 14 Ora (Voe'NQosTEL HORNBOSTEL DIAPHRAGM UNIT Sept. 4, 1951 4 Sheets-Sheet 4 Filed July so, 1945 [nVEnZ UF 11.0 r0 #wemeasrs;

\\\\\\\\\\\ www Patented Sept. 4, 1951 UNITE-PD PATENT OF FICE oyd fi r s '7 1b1t i asset: to e .Iron worksyBloig-wis, a corporation of wisconsin anesthetist in; 194.5. sesame-601 128 This invention relates to a dial'ihiaQhlQilIiit. and more particularly to a diaphragm unit for use with a roll assemhlymapaper ma mg machine' in which the amount of pressure cally applied to maintain the dfisi fedjamountjof pressure contact between the r0115 acts ,throiigh and is controlledjby' a gaseous fluid actuated'diaphragm. a Heretofore ithas'been customary to dontrol the amount of pressure contact between press rolls and the like by the use orpressureapplyiaenieeh-' anisms acting through resilient ,rneans, such a;s' springs. Such mechanical pressure applying mechanisms, however; are 1 i i l i c1il,t to so loontilql and operate .as to .maintain' .the desired pressure contact uniformly along the'gline Lor area of contact betweenthe-rolls. lIt isalso difiicult m a such mechanical pressure loading device at the Siame'pressure, orratnsome.other'desiredp urje';

when starting ,up again one run of the time weight and grade of paper',or of .a diifereiitweight and grade of paper. ,Inasmuch aslthe strength and other characteristicsiof.the paper web depend quitelarge yun nwtheimain enancerq ithfi q e'r degree of pressure 'loadingjbetweenfthepressrolls or other pressurecontact rolls between whioh the web isto be pa'ssed,,it isthighlyimportaht tha't.thef

proper amount of 'pressure hesmalntained a ,all times during theop'eration. of ,the -m a,chin

.In accordance with theprinciplespfrmypljeseiit invention, I provide ,apre'ssurejloa 'ng, rr echaF- nism that includes a. mechanically oper'ategp s5 sure applying device, such ,a: hand @or ower Operated jack, and a -qgaseoilsflfiuid operated dia; phragm through whichthe echanically' operat:

ed device applies pressure to the movable rollj gf the rollassenihly. ,Inthe operationpf myflfiuid pressure controlledlroll assembly 1 .,t 11.e', 'd 'g'm ispreeloaded to the desired extent andwh mechanically operated pressure. applying;

means, until the amount ofthe pre loadmgohjlifi diaphragm is being transmitted .to the movalg le' rollof the assembly. ,ln orderlkqdetcl 6.1 this is the case, the-gaseous flfluid, actuated dia phragm is provided with lindicating means j for indicatingto the operator that the diaphragm in the .pre-determineclgor .nrmal,,p on .at

which. exactly the ..am unt of t the ",prel d;

t ro ls ofitheassembl can-be coniro ledtww exactly and can be varied at will. t It is. therefore;.anlimportantsobject ofthis invention to provide a diaphragm unit for use in GOhan'ie (on, h diap a is being ins m nate Jae elit -r011; assembly. "Inlthis'way the loading pres reo'n" Claims. (Cl. 267 1) .f uidz e urei ontrol d p .a emb eathe making machine, or other .fabric processing inacliine. in whi d a hr m uni means lu in axially defiectafole members are provided jorim- Pa ti a e a t bi t to .th lini wi aut b stantially resisting axial movement of the diet.- Phragrri itsel .O l e an ur mp tan ob e t- 9 thi nven n will be a p n from the .d s 'o urss (4'0 nism operated, either manually or hy er" the specification and the accompanying draw.- ines. V

lAlsshown on the drawings:

Figure 1 is a schematic showing side elevation of a portion of a paper making machine in which are' installed .a vplurality vof fluid p ffifisure en olle' o a fi i s embod i th Prieciplesof my invention.

type paper making machineha portionof one side fra 1: 2 whi hii i i ated-b h -rei rei q al ni ra 1.! ac d f m inc l id w ri e i me members I 2 and; [.3 supported upona flooris L4 and a hor onta fra m mbe A .1 1?- ported by said upright gamer members {-2 and lt. I ..-W. hl ha t Sh wi fi f 1 hemai w i f S .hem a .1y sh wn en as men -roll; it. o er which the forming wire I] travels, and a-lower ,v mi .8 m ae ate of the u e sea +991 1 said'Wi're i-l-j h ,ure spamt eid m ne-wir I] carries the web of fibrous material formed h r mid ea i s hear P es iel g iihe i helde im an of a ssur 1011111 Th w fi if uswehi thus h ,iel 0 's h i as e Ph ses tween the rolls 2| and t5, and is car I M eltint -ih fir trre ss vl a on; n i i e erallyhvt ett r P! f S'aidfirst presfs' t r0 11 assembly .P' includes Qan upper movable press roll 22 and a lower stationary ai tir suction press roll 23. A bottom press felt 24 is trained through the nip between the rolls 22 and 23 of the first press roll assembly P. Felt guide rolls 25, 26 and 21, and felt press rolls 28, 29 serve to guide the lower press felt 24 through a pre-determined path.

After passing through the first press assembly P, the top press felt 28, with the wet web carried on the under surface there-of, passes around a guide roll 30 into the nip between a lower pressure transfer roll 3| and the large Yankee drier Hi. The moist web is transferred from the felt 25 by means of the pressure transfer roll 3| to the highly polished surface of the Yankee drier drum H]. As the drum |ll revolves with the paper web in contact therewith, the paper web is dried, or partially dried, and is then stripped from the surface of said drum for further processing. As shown, the paper web W is stripped from the surface of the Yankee drier drum by means of a creping doctor 32, but the particular manner of stripping the web W from the surface of the roll forms no part of the present invention.

After leaving the nip between the pressure transfer roll 3| and the drier drum in, the felt 20, now bare, passes under and over guide rolls 33 and 34 and into a felt press assembly, indicated generally by the letters FP. The purpose of this press assembly is to extract water from the felt before it returns to the nip between the couch roll it and the pressure transfer roll 2|. leaving the press roll assembly FP, the felt 28 is guided by means of guide rolls 35, 36, and 38 back to the pressure transfer roll 2|.

It will be noted that each of the press roll assemblies P and FF, as well as the roll assembly including the pressure transfer roll 3| and the Yankee drier drum ID, includes a device for maintaining pressure between the movable roll and the stationary roll of each of these assemblies. The pressure applying mechanisms are indicated by the letter M in the first press roll assembly P; by the letters TM in the'transfer rolldrier drum assembly; and by the letters FM in the felt press assembly FP. These various pressure applying mechanisms will later be described with greater particularity.

The felt press assembly FP comprises a lower suction press roll 39 mounted upon the side frame members l and an upper movable plain press roll 48 supported at its ends by pivotally mounted arms 4|. Each of said arms 4|, of which only one is shown, is mounted at one of its ends by means of a pivot pin 42 froma support 43. The ends of said upper plain press roll 48 are journalled in bearing brackets 44 depending from the under sides of said pivotally mounted arms 4|. The other end of each said arms 4| extends beyond the bearing brackets 44 and is bifurcated, as at 45 (Figs. 1, 2 and 4) As best shown in Figures 2 and 4, the bifurcated end 45 of each of said arms 4| is formed with an apertured cylindrical portion 45a for receiving a pin 48 connecting said arm to the central hub portion 41 of a double diaphragm mechanism, indicated generally by the reference numeral 48. Cotter pins 49 pass through the extended ends of said pins 46 to hold the pins in place. The pins 48 thus provide a swivel mounting between the bifurcated ends 45 of the arms 4| and the hub portions 41 of the diaphragm mechanisms 48.

Said diaphragm mechanisms 48 have pressure transmitting rods 50 connecting them with mechanically operated jacks 5| (Fig. 1).

After Each of the jacks 5| has a manually operable crank arm or handle 52 for turning a shaft 53, the inner end of which extends into a casing 54 and carries a pinion (not shown) for meshing with a pinion or worm on the lower end of the connecting rod 5|]. Instead of providing for manual operation of the shaft 53, said shafts 53 may be connected to suitable power means for operating thejacks 5|. Thedetailed operation of the jacks 5| will be obvious from the foregoing description .1 0, anyone familiar with such mechanisms.

As best shown in Figures 2 to 4, inclusive, each "of "the diaphragm mechanisms 48 includes a ed through websj14 and 15 to the hub portion frame comprising a pair of upper and lower straps 48a. and 48b, respectively, the ends of which are joined together by means of adjustable tie rods 48c and 48d. Said tie rods 48c and 48d 'are threaded at their ends for reception into internally threaded end sockets 55 and 56, respectively, formed on said straps 48a and 4%. Nuts 51 and 58, and 59 and 60 are provided for securing the ends of said rods 48a and 48b within said end sockets 55, 55 and '56, 56. The straps 48a and 48b,"an'd the tie rods 48 and 4811, thus form a rigid frame.

The upper strap 48:]. has a central enlargement 6| fromwhich depends an integral circular plate 62." The central portion of a diaphragm 63 is clamped against the under side of said circular plate 62 by means of a smaller circular plate 64 L and screws 65. The outer periphery of said diaphragm 63 is clamped against the upper surface of a peripheral flange B8 of a downwardly concave casing member 61 by means of a ring 68 and screws 69. Said diaphragm 63 thus forms the upper wall of a chamber 10 within the concavity of the casing member 61. A pipe 1| serves for the admission of a gaseous fluid under pressure into said chamber 18. inner wall 'of the casing member 61 are provided with normally spaced, aligned abutments 12' and 13, respectively, for the purpose of limiting the relative movement toward each other of said diaphragm 63 and casing member 61.

The said casing member 61 is integrally connect- 41 betweenthe previously described bifurcated ends 45., and by continuations of said Web portions to a casing member 16 forming a part of thelower diaphragm portion. Said casing memher-11$ is upwardly concave and formed with a downwardly'extending annular flange 11, against which is clamped a diaphragm 18 by means of a ring 19 and screws 80. Said diaphragm 18, like the'diaphragm 63, is formed of suitable flexible,

- resilient material, such as a natural rubber or synthetic rubber composition or the like.

The central portion of said diaphragm 18 is clamped between-an upper circular plate 8| and a lower, larger circular plate 82 by means of screws 83. The upper plate 8| and the inner surface of the casing member 16 are provided withopposed aligned abutments 84 and 85, respectively. These abutments serve to limit relative movement toward each other of the casing member 16 and diaphragm 18. The lower plate limits the amount of insertion of said threaded rod end into the socket 81 and also serves to hold the rod and socket portion against separation.

7;; order to give lateral stability to the dia- The lower plate 64 and the phragms 6 3 and 18, pairs "of spring arms as and 99 are connected, respectively, between the circular plate 62 and the 68 and between the circular plate 82 and the ring HI. the case of the pair of springs 89, the outerends of said springs are secured by means of bolts 91 to the ring 68 and the inner ends are secured to the circular plate '52 by means "of bolts 92. In the case of the lower pair of springs "90, the outer ends of said springs are bolted to the ring 19 by means of bolts 93 and to the circular plate 82 by meansof-bolts94.

Each pair of springs 89 and 90 comprises relatively thin, flat, elongated strips "of an elastic material, such as the laminated plastic material known as Micarta.- The springs are very stable laterall but are at 'the same time very flexible in the direction-bf movement of the diaphrag'ms. If the diaphragms were made rigid laterally, they would also have to 'be rigid in their direction of movement, which is something that is not desirable. The main purpose of the diaphragm units is to have the units act as a cushion, a thing that is possible through the use of a compressible-gas such as air.

The lower casing member -T6 forms with the diaphragm 18 a chamber 95, into which airor other compressible gas is introduced througha pipe 96. In usual practice air is the gaseous fluid used in the diaphragm chambers "I and 95. Compressed air from a suitable source is conducted through a pipe line 9! to branch lines 91a and 97b for admission through the pipes II or 96 into the diaphragm chambers I0 or '95. Reducing valves 98a and 98b in said branch lines 91a and 91b serve toregulate the air pressure in said chambers to the desired amount, which may be indicated by pressure gauges 99a and 9%.

Where it is desired to apply anadditional loading pressure at the nipbetweenthe'rolls 39 and 30, above that supplied by the weight of roll 49, the air pressure in the chamber III is brought up to the desired amount, and then the jack 5I is-operated to bring the top roll 40 into contact with the bottom roll 39. Thereafter, the jack BI is further operated so that the mechanism is in its mid-position as shown in Fig. 4, namely with clearance between the abutments I2 and 13 and between the abutments M and 95.

Such mid-positioning of-the diaphragm -mechanism is determined when *a'pointez; I90 (Fig.2) registers with the bottom race of an adjustable collar I001. The collar IDIla is movable along the rod 54 into its properly adjusted position where it is held by means nf a set screw Illilb. When the pointer hill-is opposite the lower face of the collar Ifllla, the diaphragm pressure mechanism will be in its normal position asillu'strated in Figure 4. When fin this :positiongthe pre-determined air pressure within ;the chamber will automatically determine the-nip loading pressure between the press rolls "39 :and 40.

In some instances, it may :be tdesirable to reduce the nip pressure between the lpressure'rolls 39 and 49 below that produced bylthe weightlof the top roll 40. In that tcase :air is .admitted under pressure into the chamber '95 to .build up the desired pressure therein to 'oflfsetla portion of the weight of the .top:roll 40, and 'thusaobtain the required nip pressure. The ijack 5| is then operated to bring the diaphragm pressure mechanism into mid-position:again.

The abutments "l2 #and 13 "and :84 and :85 prothe diaphragm's .63 and l8 toward the bottoms of their respective casing members 61 and "Hi. The diaphragms '63 and 18 are, of course, prevented from being blown up like balloons by the fact that the straps 48a and 48b, held together as they are by the rods 48c and 48d, limit the outward movements of said diaphragms.

'When the diaphragm pressure mechanism is brought into its mid-position, as previously :described, the applied nip loading pressure between the rolls 39 and 40 is solely that due to the .air pressure within the chambers 10 or 95. In that position, the end of each loading arm AI is maintained in a floatingstate between the air cushions within said diaphragm chambers. There is-thus produced a very-constant and uniform, as well as a resiliently applied, loading pressure at the nip between said rolls 39 and 40. Should the amount of pressure change for any reason, the operator can determine that visually by inspection of the indicating-gauge 99a or 9%.

Referring now to the gaseous fluid pressure controlled mechanism for controlling the nip pressure between the pressure transferrolltl and the drier drum ill, said roll 3| is supported from one end of a pressure transmitting rocker arm 'I'G'I. There are two such arms IIlI, one ateach side of the machine for supporting the respective ends of the roll 3i. Each of said arms -l-0I is pivoted intermediate its ends, as at 102, from the upright frame member 12. The outer'end H33 of each of 'saidro'cker arms IllI carries a'bearing housing I04, in which one of the ends of the rolls *3 I is journalled. Each of said end bearing housings I04 carries a dependent arm -I 05 for journalling one end of the felt guide roll 39.

The other ends of the rocker arms IOI are connected to the diaphragm mechanism-s TM. Said mechanisms, as best shown in Figures -1, 5,

i 6 and '7, are connected-by depending rods Hi6 to jacks I91. The jacks III! are similar in opera-- tion to the jacks 5I, previously described. They maybe either manually'operated as by means'of handles I08, or power operated, and .serve :to raise or lower the rods I06. The jacks II]? are supported from the horizontal side frame member I5 on either side of the machine.

The lower end of each of the rods I06 is'secured in a socket I99 (Figs/5 and 6) of an upper casing member IIO. Said casing member I=-I-il is provided with a lower annular-flange II I,to which is peripherally clamped a diaphragm I I2 by means of a ring II-3 and'screws I I4. The central portion'of the diaphragm II? is clamped between a small=diameter upper circular plate H5 and the enlarged upper disk-like face H 6 or a hollow cylindrical member III. Screws IIG extend through said upper circular plate -Ii5, the diaphragml-I l andinto the upper enlarged walls we of the-member H7. The lower cylindrical portion of'said member I I1 is swivelly secured in arr-end socket I20 carried by the 'freeend'of-therccker arm IOI.

-A pair of flat springs I--2I, similar to the diet springs previously described, are secured to the ring I l3by means of bolts I22 andto the-underside of the circular plate H6, .asby means .of bolts Q3. The casing member III) and :diaphragm I I2 provide a chamber I-24,-into which a gaseous fluid :under pressure may be admitted through a pipe I 25.

The upper-inner wall of the casing --member Hi9 iislprovided with an abutment .1126 .to -serve as a;stop:.for limiting the movementlthereagainst yide stops that limit thexrelativemmovements lof of the upper circular plate I I5.

' The ring I I3 is provided along diametrically opposed portions of its arc with a downwardly and inwardly directed flange I2'I which serves to limit the downward movement of the plate H6. The ring II3 (Fig. '7) is also provided with anintegral, laterally extending arm I28, from the end of which depends a reference pin I29. Said reference pin I29 has a threaded upper end I33, which is threaded through said arm I28 and held in place therein by means of a nut I3 I.

An upwardly flanged plate I32 is fixedly mounted upon the cylindrical member III beneath the diaphragm. Said plate I32 is of such diameter that its upwardly turned annular flange I33 lies in spaced relationship to the ring 3. As illustrated in Figure '7, said flange I33 has a pointed projection I34 that serves as a reference for the lower edge of the pin I29. When said lower pin edge and pointed projection I34 are in registration, as illustrated in Figure 7, the diaphragm I I2 is then in its normal, or mid-position.

As shown in Figures 1, and 6, the casing member III] is cooked with respect to the horizontal. This is due to the fact that there is a certain amount of angular movement between the upper and lower portions of the diaphragm mechanism when the pressure roll 3| is moved. As the pressure roll is lowered, the diaphragm tends to cock the other way and it goes from this cocked position, as illustrated in Figure l, to a neutral position and then is cocked over the other way after the pressure roll has been lowered the full amount. The purpose of initially cocking the parts is to bend the diaphragm one-half of the total amount each side of its normal center line.

As previously described, air is introduced through the pipe I25 into the chamber I24 under the desired pressure, and then the jack III? is operated to bring the pressure roll 3| up against the drier drum III. This lift is continued until the diaphragm II2 comes to its midor normal position and the pressure roll pressure is controlled by means of air. In this way the full flexibility of the diaphragm under air pressure is realized for the actual loading of the pressure roll at the nip between said pressure roll and the drum I0.

As illustrated, the pressure transfer roll 3I is a suction roll, being connected to a suitable source of vacuum by means of an exhaust conduit I 43. The position of the suction chamber within said roll 3I is indicated in dotted lines at I4I (Fig. l)

In the gaseous fluid actuated diaphragm mechanism indicated at M (Fig. 1), the upper press roll 22 is suspended by means of brackets I42 from the under sides of a pair of pivotally mounted arms I43. Each of said arms I43 is pivoted, ,as at I44 to the lower end of a bracket I45, which, ,in turn, is suspended from the horizontal side frame member I3. The free end of each arm I43 is pivotally connected, as at I46 to a rod I41 that connects to a diaphragm unit I48.

The diaphragm unit I48 is of somewhat different construction from that already described. In this case the casing of the diaphragm unit I48 is connected by means of U-shaped arms I49 to the upper end of the screw I50 of a manually operable jack Iiii. As in the previous unit, the diaphragm of the unit H8 is pre-loaded by the introduction of air into the diaphragm chamber under the desired pressure, and the jack I5I is operated until the diaphragm assumes its normal position. In this way, the desired loading pres.- sure is applied at the nip between the rolls 22 and 23.

It will thus be apparent that in all the various forms of my invention, I impose the desired amount of loading pressure upon the diaphragm and then operate the mechanically actuated jack, or other pressure-applying means, to bring the diaphragm into its. normal or mid-position, at which the loading pressure is transmitted to the nip between the pressure rolls. I thus utilize the full flexibility of the diaphragm with a suflicient air pressure for the actual loading of the pressure rolls.

The stop provided by the abutment I26 and plate II5 prevents the pressure roll 3| from dropping more than a slight distance if the pressure on the diaphragm should drop or the diaphragm break. On the other hand the stop provided by the flanges I21 for the plate IIIS prevents the diaphragm from being blown up like a balloon and broken -by air pressure when the screw device In! is operated to drop the pressure roll 3I 'away from the drier drum Ill.

It will, of course, be understood that various details of construction may be varied through a wide range without departing from the principles of this invention and it is, therefore, not the purpose to limit the patent granted hereon otherwise than necessitated by the scope of the appended claims.

I claim as my invention: 7

1. A diaphragm unit comprising a concave casing having an annular flange, an annular clamping ring secured to said casing flange, a diaphragm clamped at its periphery between said flange and said ring to form with said casing a gas pressure chamber, rigid circular members holding the central portion of said diaphragm clamped therebetween and cantilever springs extending generally parallel to the normal plane of said diaphragm and having one end secured to one of said circular members and the other end secured to said clamping ring to impart lateral stability to said unit without substantially resisting axial movement of said diaphragm.

2. A diaphragm unit comprising a casing for connection to a force applying member, said casing having an annular peripheral flange, an annular clamping ring secured to said casing flange, a diaphragm having its periphery confined be tween said flange and said ring for cooperation with said casing to provide therewith a gas pressure chamber, means for introducing into said chamber a gas under pressure, rigid means clamping the central portion of said diaphragm and adapted to be connected to a force transmitting member, flat springs resiliently connecting said rigid clamping means to said casing flange and ring assembly and extending substantially parallel to each other ,end to said diaphragm to impart lateral stability of said unit without substantially resisting axial movement of said diaphragm, said diaphragm lying in the plane of said casing flange and said springs being adapted for flexing movement only in the plane of movement of said diaphragm to retain the parallel relationship between said diaphragm and said springs, and stop means carried by said casing for movement t lerewltn and contacting said rigid means for limiting the axial movement of said diaphragm in either direction.

3. A diaphragm unit comprising a casing for connection to a force applying member, a diaphragm clamped to said casing to provide therewith a gas pressure chamber, means for introducing into said chamber a gas under pressure, rigid means clamping the central portion of said diaphragm and adapted to be connected to a force transmitting member, resilient cantilever springs defiectable only in the direction of axial movement of said diaphragm connecting said clamping means to said casing and extending substantially parallel to each other and to said diaphragm to impart lateral stability to said unit Without substantially resisting axial movement of said diaphragm, and means indicating the normal position of said diaphragm when applied transmitted forces are balanced by the desired amount of gas pressure within said chamber, said last-mentioned means including a reference member fixed to said rigid means and an indicating finger carried by said casing for movement therewith into alignment with said reference member when said forces are balanced.

4. A diaphragm unit comprising a concave circular casing having an annular flange, an annular clamping ring secured to said casing flange, a circular diaphragm clamped at its periphery between said flange and said ring to form with said casing a gas pressure chamber, a rigid circular member backing the central portion of said diaphragm to leave a narrow unbacked annular diaphragm portion and laterally rigid, axially deflectable members lying on either side of the center of said backing plate and extending generally parallel to each other and to the normal plane of said diaphragm and having one end secured to said circular member and the other end secured to said clamping ring to impart lateral stability to said unit without substantially resisting axial movement of said diaphragm.

5. A diaphragm unit comprising a concave cas ing having an annular flange, an annular clamping ring secured to said casing flange, a diaphragm clamped at its periphery between said flange and said ring to form with said casing a gas pressure chamber, rigid circular members holding the central portion of said diaphragm clamped therebetween and cantilever springs comprising relatively thin and wide strips of laminated plastic material, each of said cantilever springs extending generally parallel to the normal plane of said diaphragm and each being connected at one end to said annular clamping ring and at the other end to one of said circular members to impart lateral stability to said unit without substantiall resisting axial movement of said diaphragm.

LLOYD HORNBOSTEL.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 598,982 Egger Feb. 15, 1898 737,154 Sayer Aug. 25, 1903 1,111,739 Davis Sept. 29, 1914 1,328,496 Cox Jan. 20, 1920 1,461,497 Robins July 10, 1923 1,467,986 Van Der Pyl Sept. 11, 1923 2,021,043 Bedford et al Nov. 12, 1935 2,023,135 Hawkins Dec. 3, 1935 2,357,299 Bagnall Sept. 5, 1944 2,364,443 Hornbostel Dec. 5, 1944 2,452,176 Bent Oct. 26, 1948 FOREIGN PATENTS Number Country Date 698,111 Germany Nov. 1, 1940 528,105 France Aug. 9, 1921 814,849 France Mar. 30, 1937 OTHER REFERENCES Product Engineering, Feb. 1943, pages 112, 113. 

